Method of converting a system generating saturated steam, having at least one steam turbine group, and power station converted in accordance with the method
1. Field of the Invention
The present invention relates to a method of converting a system generating saturated steam, having at least one steam turbine group, into a power station designed for elevated live steam parameters. It also relates to a power station converted in accordance with this method.
2. Related Art
Various permits from the authorities, which have to be awarded at time intervals, are necessary for the building, commissioning and operation of a nuclear power station. For a wide variety of reasons, in particular a change to the political situation, it can occur that no operational permit is awarded for a completely finished nuclear power station or that a permit already awarded is withdrawn. It is also known for governments to operate a withdrawal from nuclear power station technology. The result of this can be investment catastrophes involving an intact water/steam circuit, electrical installations, buildings, cooling water installations, etc.
One possibility for the further utilization of the conventional installation constituent consists in converting the nuclear power station into a combined power station.
In the course of such a conversion from systems generating saturated steam, having steam turbine groups, an effort is made to carry out a conversion into a power station with more elevated steam parameters and involving steam turbine groups designed for more elevated steam parameters in order, by this means, to increase the efficiency of the complete power station, which comprises the system generating saturated steam and the steam turbine groups.
The invention is therefore based on the object of creating a method of converting a system generating saturated steam, having at least one steam turbine group which has a saturated-steam medium-pressure steam turbine, according to which method a maximum possible part of the original installation technology can continue to be used.
This conversion should, advantageously, be associated with an increase in the power but, at the same time, also with an increase in the efficiency of the overall power station.
The invention finds particular application in the conversion of nuclear power stations whose nuclear installation part has to be put out of action and, subsequently, possibly dismantled.
In accordance with the invention, this is achieved in a first embodiment of the method by the system generating saturated steam being replaced by at least one gas turbine set, at least one waste-heat boiler and at least one back-pressure steam turbine, by the exhaust gas of the at least one gas turbine of the at least one gas turbine set being used for generating steam in the at least one waste-heat boiler, by the steam generated in the at least one waste-heat boiler being supplied via a live-steam line to the at least one back-pressure steam turbine and by the exhaust steam of the at least one back-pressure steam turbine being made available for the supply to the at least one steam turbine group, preferably to a saturated-steam medium-pressure steam turbine of the steam turbine group. The exhaust steam conditions of the at least one back-pressure steam turbine correspond essentially, in accordance with a preferred embodiment, to the previous steam parameters at the inlet to the existing steam turbine group. In this first embodiment, the complete steam turbine group is retained in its previous form.
In a second embodiment of the method, the design of the at least one waste-heat boiler and of the at least one back-pressure steam turbine is modified in such a way that the steam parameters between back-pressure steam turbine and saturated-steam medium-pressure steam turbine are displaced to more elevated temperatures and lower pressures within the ranges permissible for the saturated-steam medium-pressure steam turbine and in such a way that the final expansion point at the outlet from the saturated-steam medium-pressure steam turbine is moved to lower steam wetnesses and, if possible, into the superheated range, in such a way as to dispense with the separator and also, if possible, the reheater between saturated-steam medium-pressure and low-pressure steam turbines.
In a third embodiment of the method, the replacement occurs in each case by means of a waste-heat boiler with reheater, the saturated-steam medium-pressure steam turbine of each steam turbine group being replaced by at least one new medium-pressure steam turbine designed for more elevated steam parameters, the exhaust steam from the at least one back-pressure steam turbine being made available for supplying the reheater of the at least one waste-heat boiler, this steam being reheated and the reheated steam being made available for supplying the at least one new medium-pressure steam turbine. The new medium-pressure steam turbine is advantageously designed in such a way that the parameters of its exhaust steam are at least approximately equal to the steam parameters at the inlet to the low-pressure steam turbine of the original steam turbine group, so as to dispense with the separator, and if possible also the reheater between the new medium-pressure steam turbine and the low-pressure steam turbine.
A power station converted according to a first version of an installation for carrying out the method and containing at least one steam turbine group having a saturated-steam medium-pressure steam turbine, a separator, a reheater operating with saturated steam, and a low-pressure steam turbine, is characterized by at least one gas turbine set, at least one waste-heat boiler and at least one back-pressure steam turbine as replacement for the original system generating saturated steam, and by the at least partially retained at least one steam turbine group of the original power station.
According to a second version of the installation for carrying out the method, the at least one waste-heat boiler and the at least one back-pressure steam turbine are designed in such a way that the steam parameters between back-pressure steam turbine and saturated-steam medium-pressure steam turbine are located within the ranges of high temperature and low pressure which are permissible for the saturated-steam medium-pressure steam turbine, and in such a way that the final expansion point at the outlet from the saturated-steam medium-pressure steam turbine is located within the ranges of steam wetness which is lower than that of the original power station. It is then possible to dispense with the separator of the original power station. A further embodiment provides for parameter ranges specified in such a way that the final expansion point at the outlet of the saturated-steam medium-pressure steam turbine is located within a range of superheated steam so that, in addition, it is also possible to dispense with the superheater.
A third configuration of the installation for carrying out the method is characterized by at least one gas turbine set, at least one waste-heat boiler with reheater, at least one back-pressure steam turbine and at least one medium-pressure steam turbine as replacement for the original system generating saturated steam and the saturated-steam medium-pressure steam turbine, the steam parameters at the outlet from the reheater being specified in such a way that, in the converted power station, the at least one steam turbine group is retained with a new medium-pressure steam turbine adapted to the parameters at the outlet from the reheater, and without separator and without reheater.
The advantages of the invention may essentially be seen in the fact that a nuclear power station, in particular, can be converted to a combined power station with minimum investment while continuing to retain, as far as possible, the conventional installation technology, and a power station can be obtained whose power and whose efficiency are higher than those of the original nuclear power station.